Nikola A. Bowden

Dysregulation of miRNA 181b in the temporal cortex in schizophrenia

Analysis of global microRNA (miRNA) expression in postmortem cortical grey matter from the superior temporal gyrus, revealed significant up-regulation of miR-181b expression in schizophrenia. This finding was supported by quantitative real-time RT-PCR analysis of miRNA expression in a cohort of 21 matched pairs of schizophrenia and non-psychiatric controls. The implications of this finding are substantial, as this miRNA is predicted to regulate many target genes with potential significance to the development of schizophrenia. They include the calcium sensor gene visinin-like 1 (VSNL1) and the ionotropic AMPA glutamate receptor subunit (GRIA2), which were found to be down-regulated in the same cortical tissue from the schizophrenia group. Both of these genes were also suppressed in miR-181b transfected cells and shown to contain functional miR-181b miRNA recognition elements by reporter gene assay. This study suggests altered miRNA levels could be a significant factor in the dysregulation of cortical gene expression in schizophrenia.

Preliminary investigation of gene expression profiles in peripheral blood lymphocytes in schizophrenia.

Schizophrenia is a heterogenous disorder that is phenomenologically characterised by a combination of negative, positive, and cognitive symptoms with variable expression in the course of illness. Here, we investigated differential gene expression in relation to age to address the heterogeneity of this disorder We used 6000 gene cDNA microarrays to generate gene expression profiles from peripheral blood lymphocytes from 14 individuals with schizophrenia and 14 non-psychiatric controls. Genes showing altered expression were identified and 18 genes with brain-related functions were altered, 4 of which, endothelial differentiation gene 2 (Edg-2), ezrin-radixin-moesin phosphoprotein 50 (EBP50), Myc-associated zinc finger protein (MAZ) and Tumor Necrosis Factor Receptor 2 (TNFR2), were confirmed by relative real-time PCR. Dendrograms were constructed using genes that showed significantly different expression (p<0.05) between groups based on median split of age dividing the matched pairs into distinct subclasses. Our findings suggest that distinct gene expression profiles in peripheral blood lymphocytes associated with schizophrenia phenotypes may provide a first step towards the biological classification of schizophrenia subtypes. The validity of this approach may lead to better methods of defining this enigmatic disease.

BRIP1 , PALB2 , and RAD51C mutation analysis reveals their relative importance as genetic susceptibility factors for breast cancer

Mutations in the recognized breast cancer susceptibility genes BRCA1, BRCA2, TP53, ATM, and CHEK2 account for approximately 20% of hereditary breast cancer. This raises the possibility that mutations in other biologically relevant genes may be involved in genetic predisposition to breast cancer. In this study, BRIP1, PALB2, and RAD51C were sequenced for mutations as a result of previously being associated with breast cancer risk due to their role in the double-strand break repair pathway and their close association with BRCA1 and BRCA2. Two truncating mutations in PALB2 (Q66X and W1038X), one of which is has not been reported before, were detected in an independent Australian cohort of 70 individuals with breast or ovarian cancer, and have strong family histories of breast or breast/ovarian cancer. In addition, six missense variants predicted to be causative were detected, one in BRIP1 and five in PALB2. No causative variants were identified in RAD51C. This study supports recent observations that although rare, PALB2 mutations are present in a small but substantial proportion of inherited breast cancer cases, and indicates that RAD51C at a population level does not account for a substantial number of familial breast cancer cases.

IL-27/IFN-γ Induce MyD88-Dependent Steroid-Resistant Airway Hyperresponsiveness by Inhibiting Glucocorticoid Signaling in Macrophages

Inflammation and airway hyperresponsiveness (AHR) are hallmark features of asthma and often correlate with the severity of clinical disease. Although these features of asthma can be effectively managed with glucocorticoid therapy, a subgroup of patients, typically with severe asthma, remains refractory to therapy. The mechanisms leading to steroid resistance in severe asthmatics are poorly understood but may be related to the activation of innate host defense pathways. Previously, we have shown that IFN-γ–producing cells and LPS, two factors that are associated with severe asthma, induce steroid-resistant AHR in a mouse model. We now demonstrate that cooperative signaling induced by IFN-γ and LPS results in the production of IL-27 by mouse pulmonary macrophages. IL-27 and IFN-γ uniquely cooperate to induce glucocorticoid-resistant AHR through a previously unknown MyD88-dependent mechanism in pulmonary macrophages. Importantly, integrated signaling by IL-27/IFN-γ inhibits glucocorticoid-induced translocation of the glucocorticoid receptor to the nucleus of macrophages. Furthermore, expression of both IL-27 and IFN-γ was increased in the induced sputum of steroid-refractory asthmatics. These results suggest that a potential mechanism for steroid resistance in asthma is the activation of MyD88-dependent pathways in macrophages that are triggered by IL-27 and IFN-γ, and that manipulation of these pathways may be a therapeutic target.

Nucleotide excision repair: why is it not used to predict response to platinum-based chemotherapy?

Platinum based therapy is one of the most effectively used chemotherapeutic treatments for cancer. The mechanism of action of platinum compounds is to damage DNA and drive cells into apoptosis. The most commonly used platinum containing agents are cis-diammine-dichloroplatinum (II)], more commonly known as cisplatin, its analogue carboplatin, and oxaliplatin. Cisplatin is used to treat a wide variety of tumours such as ovarian, testicular, head and neck and non-small cell lung cancers (NSCLCs). In addition, it forms the basis of most combined treatment regimes. Despite this, cisplatin and its analogues are extremely toxic and although some patients benefit substantially from treatment, a large proportion suffer the toxic side effects without any therapeutic benefit. Nucleotide excision repair (NER) is a versatile DNA repair system that recognises DNA damage induced by platinum based therapy. For many years the components of the NER pathway have been studied to determine mRNA and protein expression levels in response or resistance to cisplatin in many forms of cancer; particularly testicular, ovarian and NSCLCs. Despite the consistent finding that over or under expression of subsets of NER proteins and mRNA highly correlate with response to cisplatin, the translation of these findings into the clinical setting has not been forthcoming. This review summarises the results of previous investigations into NER in cisplatin response and clinical trials where the expression of NER proteins were compared to the response to platinum therapies in treatment.

Differential gene expression and cytokine production from neutrophils in asthma phenotypes.

Asthma is characterised into eosinophilic and non-eosinophilic phenotypes based on inflammatory cell patterns in airway secretions. Neutrophils are important in innate immunity, and are increased in the airways in non-eosinophilic asthma. The present study investigated the activity of neutrophils in asthma phenotypes. Participants with eosinophilic (n = 8) and non-eosinophilic asthma (n = 9) and healthy controls (n = 11) underwent sputum induction and blood collection. Neutrophils were isolated and cultured with or without lipopolysaccharide. Cytokines were measured by ELISA, and gene expression was analysed using a gene expression microarray and quantitative PCR. In non-eosinophilic asthma, blood neutrophils released significantly higher levels of interleukin-8 at rest. Cytokine gene expression and sputum neutrophil protein production did not differ between asthma subtypes. Microarrays demonstrated closely related expression profiles from participants with non-eosinophilic asthma that were significantly distinct from those in eosinophilic asthma. A total of 317 genes were significantly altered in resting neutrophils from participants with non-eosinophilic asthma versus eosinophilic asthma, including genes related to cell motility and regulation of apoptosis. Non-eosinophilic and eosinophilic asthma are associated with specific gene expression profiles, providing further evidence that these phenotypes of asthma involve different molecular mechanisms of disease pathogenesis at the systemic level. The mechanisms of non-eosinophilic asthma may involve enhancement of blood neutrophil chemotaxis and survival.

P53 in human melanoma fails to regulate target genes associated with apoptosis and the cell cycle and may contribute to proliferation

BackgroundMetastatic melanoma represents a major clinical problem. Its incidence continues to rise in western countries and there are currently no curative treatments. While mutation of the P53 tumour suppressor gene is a common feature of many types of cancer, mutational inactivation of P53 in melanoma is uncommon; however, its function often appears abnormal.MethodsIn this study whole genome bead arrays were used to examine the transcript expression of P53 target genes in extracts from 82 melanoma metastases and 6 melanoma cell lines, to provide a global assessment of aberrant P53 function. The expression of these genes was also examined in extracts derived from diploid human melanocytes and fibroblasts.ResultsThe results indicated that P53 target transcripts involved in apoptosis were under-expressed in melanoma metastases and melanoma cell lines, while those involved in the cell cycle were over-expressed in melanoma cell lines. There was little difference in the transcript expression of P53 target genes between cell lines with null/mutant P53 compared to those with wild-type P53, suggesting that altered expression in melanoma was not related to P53 status. Similarly, down-regulation of P53 by short-hairpin RNA (shRNA) had limited effect on P53 target gene expression in melanoma cells, whereas there were a large number of P53 target genes whose mRNA expression was significantly altered by P53 inhibition in melanocytes. Analysis of whole genome gene expression profiles indicated that the ability of P53 to regulate genes involved in the cell cycle was significantly reduced in melanoma cells. Moreover, inhibition of P53 in melanocytes induced changes in gene expression profiles that were characteristic of melanoma cells and resulted in increased proliferation. Conversely, knockdown of P53 in melanoma cells resulted in decreased proliferation.ConclusionsThese results indicate that P53 target genes involved in apoptosis and cell cycle regulation are aberrantly expressed in melanoma and that this aberrant functional activity of P53 may contribute to the proliferation of melanoma.

Altered gene expression in the superior temporal gyrus in schizophrenia

BackgroundThe superior temporal gyrus (STG), which encompasses the primary auditory cortex, is believed to be a major anatomical substrate for speech, language and communication. The STG connects to the limbic system (hippocampus and amygdala), the thalamus and neocortical association areas in the prefrontal cortex, all of which have been implicated in schizophrenia.ResultsTo identify altered mRNA expression in the superior temporal gyrus (STG) in schizophrenia, oligonucleotide microarrays were used with RNA from postmortem STG tissue from 7 individuals with schizophrenia and 7 matched non-psychiatric controls. Overall, there was a trend towards down-regulation in gene expression, and altered expression of genes involved in neurotransmission, neurodevelopment, and presynaptic function was identified. To confirm altered expression identified by microarray analysis, the mRNA expression levels of four genes, IPLA2γ, PIK31R1, Lin-7b and ATBF1, were semi-quantitatively measured using relative real-time PCR. A number of genes with altered expression in the STG were also shown to have similar changes in expression as shown in our previous study of peripheral blood lymphocytes in schizophrenia.ConclusionThis study has identified altered expression of genes in the STG involved in neurotransmission and neurodevelopment, and to a lesser extent presynaptic function, which further support the notion of these functions playing an integral role in the development of schizophrenia.

The role of altered nucleotide excision repair and UVB-induced DNA damage in melanomagenesis

UVB radiation is the most mutagenic component of the UV spectrum that reaches the earth’s surface and causes the development of DNA damage in the form of cyclobutane pyrimidine dimers and 6-4 photoproducts. UV radiation usually results in cellular death, but if left unchecked, it can affect DNA integrity, cell and tissue homeostasis and cause mutations in oncogenes and tumour-suppressor genes. These mutations, if unrepaired, can lead to abnormal cell growth, increasing the risk of cancer development. Epidemiological data strongly associates UV exposure as a major factor in melanoma development, but the exact biological mechanisms involved in this process are yet to be fully elucidated. The nucleotide excision repair (NER) pathway is responsible for the repair of UV-induced lesions. Patients with the genetic disorder Xeroderma Pigmentosum have a mutation in one of eight NER genes associated with the XP complementation groups XP-A to XP-G and XP variant (XP-V). XP is characterized by diminished repair capacity, as well as a 1000-fold increase in the incidence of skin cancers, including melanoma. This has suggested a significant role for NER in melanoma development as a result of UVB exposure. This review discusses the current research surrounding UVB radiation and NER capacity and how further investigation of NER could elucidate the role of NER in avoiding UV-induced cellular death resulting in melanomagenesis.

Altered expression of regulator of G-protein signalling 4 (RGS4) mRNA in the superior temporal gyrus in schizophrenia.

To identify altered mRNA expression of regulator of G-protein signalling 4 (RGS4) in the superior temporal gyrus (STG) in schizophrenia mRNA expression of RGS4 was measured from post-mortem STG tissue from 13 individuals with schizophrenia and 13 matched non-psychiatric controls using relative real-time PCR. Significantly decreased expression of RGS4 mRNA in the STG in schizophrenia was identified in 10 of the 13 matched pairs. Altered expression of RGS4 in cortical regions previously implicated in schizophrenia, such as the STG further supports the notion of RGS4 as a potential genetic and functional biological marker of schizophrenia.